1. Field of the Invention
The present invention relates to a torque converter system and, more particularly, to a power transmission system including a multi-stage torque converter with a vibration damper assembly interposed between a circulatory turbine member and the torque converter power output shaft and associated system components.
2. Description of the Prior Art
A variety of torque converter devices have been developed which provide for the transmission of power with the ability to change or multiply torque. The torque converter usually has an impeller, or pump member, which acts as the power input member. A turbine member acts as the output member with a reactor, or stator member, acting for torque multiplication. Typically, the torque converter is either one or two stages, where the number of stages represents the number of turbine elements. In a multi-stage torque converter, a primary or main turbine member will act in conjunction with a secondary or circulatory turbine member and a reactor to provide the desired torque multiplication.
In its conventional form, the single stage torque converter consists of the several members working in a closed fluid circuit. The impeller is rotated by the input power member and pumps fluid into the turbine. The turbine member, which is coupled to the power output shaft, absorbs the energy of the fluid by deflecting and discharging it in a backward direction. The reactor, which is fixed to the casing by a one-way clutch, provides the necessary torque reaction by redirecting the backward flow from the turbine to a forward direction to discharge it into the impeller.
The addition of a secondary turbine member, or circulatory turbine, provides an additional torque multiplication at the lower end of output speed. Typically, the circulatory turbine provides torque multiplication from the stall condition until the condition where the main turbine is running from 0.3 to 0.4 times the speed of the impeller. At that speed, the circulatory turbine blades pass their effective blading angle and thus the main turbine provides the power output and the circulatory turbine, with the provision of a one way clutch, freewheels.
Once the speed of the main turbine has nearly reached the speed of the impeller, i.e., at the high end of output speed, the turbine no longer acts as a multiplier of torque. At that point, the torque converter is typically "locked up" and acts as a direct drive between the torque converter input and output to minimize losses between the input and output from slippage and inefficiency.
In some engine and transmission applications, particularly those utilizing diesel engines, which have extreme conditions of shock and torsional disturbances, a vibrational damper assembly is provided along the driveline. The damper typically provides a means of smoothing out driveline torsional disturbances and objectional gear rattle noises. Where a damper assembly is provided in the torque converter, the damper is used as a lockup mechanism to provide a direct drive. This lockup occurs only at the high end of output speed, generally on the order of 0.8 to 0.9 times engine speed.
As a result of the essentially independent operation of the torque converter members and the damper assembly in such prior art systems, that is, operation of the torque converter members to obtain torque multiplication at the low end and operation of the damper assembly to reduce drive line disturbances at the high end, each unit requires its own independent connections to the power output. The conventional torque converter is drivingly connected to the power output through two separate connections. The main turbine member is drivingly connected to an output shaft by a hub assembly and the circulatory turbine member is separately drivingly connected to an output shaft through an extended plate assembly. Both output shafts are operatively connected to a transmission input through a gear reduction system such as planetary gears. In some prior art assemblies, a damper assembly is interposed between the main turbine element and the output shaft. In most prior art assemblies, a damper assembly is independently drivingly connected to an output shaft through a hub plate.
There has been a need for a torque converter assembly which reduces the number of pieces required for driving connection of the circulatory turbine to the output shaft. Moreover, there is a need for a torque converter assembly which avoids the use of a long, thin plate assembly for connection of the circulatory turbine to the output shaft. Such a plate assembly has failed to provide the optimum control of axial movement of the circulatory turbine with respect to the other members of the toroidal fluid circuit, and results in fluid losses in the toroidal fluid circuit. There has also been a design need for a system having less overall length.
The torque converter with integrated damper assembly of the present invention avoids these shortcomings of the prior art designs and provides the stated desiderata by eliminating the separate connection of the circulatory turbine to the output shaft and controlling the axial movement of the circulatory turbine by utilizing the rigid plates of the damper assembly for its connection.